edit: I've updated this to add support for dumping files to an XBMC server that is on a different computer than NZBGet. Now you can specify a "local path" -> "remote path" mapping so that the script doesn't ask XBMC to update a path that doesn't exist on that computer. For me, this looks like:
LocalRootPath=/mnt/media
RemotePath=smb://SERVER/mediadump
With those settings, when a movie is downloaded into /mnt/media/Movies/Really.Great.Movie, the script will send the directory to XBMC as smb://SERVER/mediadump/Movies/Really.Great.Movie, since smb://SERVER/mediadump is what I have XBMC setup to load videos from.
The latest changes also include the ability to force a full library scan when this script runs.

edit 2013-11-15: Now supports multiple XBMC servers by separating them with commas. Also some tweaks for newer versions of Python.
edit 2014-01-23: Now supports a notification image and "final dirs" for when other PP scripts have moved the resulting download. Also fixed the attached file to end in LF's instead of CRLF's. Thanks danofun and bgoldie!